A fossil unearthed in Great Britain may end a long-running debate about the molluscs, one of lifes most diverse invertebrate groups: Which evolved first, shelled forms like clams and snails, or their shell-less, worm-like relatives? The small new fossil, found in marine rocks along the English-Welsh border, provides the best fossil evidence yet that the simpler worm-like mollusks evolved from their more anatomically complex shelled brethren, rather than the other way around. Read more
Scientists have discovered a rare fossil called Kulindroplax, the missing link between two mollusc groups. It answers thee question which came first the snail or the slug, a shelled creature or unshelled mollusk. The researchers have unearthed the worm-like partly shelled Kulindroplax, which they have modelled in a 3D computer animation. Kulindroplax lived in the sea during the Silurian Period, approximately 425 million years ago, when most life lived in the oceans and the first plants were beginning to grow on land. The team found the Kulindroplax fossil, the only one of its kind in the world, in the Welsh borderland, and it is providing the evolutionary missing link between two groups of molluscs and shedding more light on the their early origins. Read more
Title: A Silurian armoured aplacophoran and implications for molluscan phylogeny Authors: Mark D. Sutton, Derek E. G. Briggs, David J. Siveter, Derek J. Siveter & Julia D. Sigwart
The Mollusca is one of the most diverse, important and well-studied invertebrate phyla; however, relationships among major molluscan taxa have long been a subject of controversy. In particular, the position of the shell-less vermiform Aplacophora and its relationship to the better-known Polyplacophora (chitons) have been problematic: Aplacophora has been treated as a paraphyletic or monophyletic group at the base of the Mollusca, proximate to other derived clades such as Cephalopoda, or as sister group to the Polyplacophora, forming the clade Aculifera